Benefits of DSC

31st October 2010

Benefits of DSC

Initial Report

Report Text:

Our yacht has a tri-lens radar reflector (at the top of the mast), an AIS receiver (not transponder), and VHF (non DSC).  We were sailing in the English Channel on port tack at 025° True on a close reach about 60° off the wind.  We were not in a traffic separation scheme.  We were showing our tri-colour light.  There was a strong east going tide so we were making good around 55°.  We had the wind vane self steering engaged.

We observed a ship on our port side. From our AIS receiver, we could identify her name and MMSI (Maritime Mobile Service Identity), and that her course was 095°, speed 17.6 knots.

As the stand on vessel, I visually observed that the angle between us and the ship appeared unchanging.  This was confirmed using AIS.  With the vessel about 1.5 miles away a large torch was directed towards the other ship in an effort to attract attention. This was repeated.  A call was made on VHF Channel 16.  There was no response.  After closely observing the course of the other ship and detecting no change, we altered course to port and tacked thus showing the green sector of our navigation light and to pass behind the vessel.  We continued to observe the other ship to make sure there was no course change.  The other vessel passed less than 0.5 NM away after our avoiding action.

CHIRP Comment:

In using a large torch to attract the attention of the other vessel, the yacht was complying with Rule 36 of the ColRegs which states If necessary to attract the attention of another vessel any vessel may make light or sound signals that cannot be mistaken for any signal authorized elsewhere in these Rules, or may direct the beam of her searchlight in the direction of the danger, in such a way as not to embarrass any vessel.”

The yacht subsequently acted prudently in determining that action was necessary to avoid collision. In the circumstances of this report, the choices were to alter course to port towards the approaching ship, and to tack, or to alter to starboard and to gybe, away from the approaching ship. Generally, the latter may be advisable, provided that the gybe can be safely carried out, as it takes the yacht away from the approaching danger. With either action, the other vessel needs to be carefully observed in case she concurrently makes a last-minute alteration of course.

The report calls into question whether an effective look-out was being kept on the ship. We sent a copy of the report, without disclosing the identity of the yacht, to the manager of the ship.

Whilst it is permissible in these circumstances for a yacht to use VHF channel 16 to make contact with a ship, it should not be assumed that the approaching ship will be keeping a listening watch. This is no longer mandatory, although many ships still do so.

The yacht had identified the ship from her AIS receiver. Had the yacht been equipped with Digital Selective Calling (DSC) radio, she could have transmitted a message specifically to that ship. This would have actuated a very audible alert signal on the bridge of the ship.

Whilst the fitting of DSC radio is voluntary for small craft used solely for leisure purposes, the UK Maritime and Coastguard Agency (MCA) strongly recommends that they do so. For more details, please refer to the MCA leaflet No 103 which can be accessed on

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